Head Work
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Staging Lane
Joined: Jan 2015
Posts: 89
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From: Atoka, Ok
Head Work Hey guys I have a set of 862 heads for a 5.3. I sent them to my shop and he ported and polished them and gasket matched them. What exactly does "port and polish" mean? I know what gasket matching is. Also, will a set of heads with this work done to them perform a lot different than stock? Thanks Guys!!
Port and polish means just that; they're ported and polished. "Ported" is when the ports will typically be sized and shaped with a carbide grinder first, then "polished" with sandpaper rolls to smooth out the rough finish. With the popularity of CNC machines nowadays, ports aren't really polished anymore unless someone hand finishes them.
Gasket Match is a term that makes me cringe though. If anything, that's a term that should have been retired or completed excluded from the LS community around 1997. As far as the old school engines, people would actually open a port up to the gasket opening. The problem is that the gasket manufacturer has no idea how big your port needs to be and are often much larger than the port, so a true gasket match causes an expansion or bulge in the port and the manifold to cylinder head flange. This is bad for airflow.
The LS engines for the most part, use an O-ring to seal rather than a gasket, so you don't want to open up a port to the O-ring groove unless you go to a custom gasket. What you really want is a Port Match, where the runner from the intake manifold to the cylinder head makes a smooth transition without the huge bulge.
Gasket Match is a term that makes me cringe though. If anything, that's a term that should have been retired or completed excluded from the LS community around 1997. As far as the old school engines, people would actually open a port up to the gasket opening. The problem is that the gasket manufacturer has no idea how big your port needs to be and are often much larger than the port, so a true gasket match causes an expansion or bulge in the port and the manifold to cylinder head flange. This is bad for airflow.
The LS engines for the most part, use an O-ring to seal rather than a gasket, so you don't want to open up a port to the O-ring groove unless you go to a custom gasket. What you really want is a Port Match, where the runner from the intake manifold to the cylinder head makes a smooth transition without the huge bulge.
Most of the time people (or porters rather) polish the exhaust runner and/or the combustion chamber. On the intake side it's best to leave a textured/rougher surface rather than a mirror polish.
And gasket matching is quite possibly the worst thing you can do on the intake side. It opens up the runner and slows down airflow into the rest of the runner. If he enlarged the rest of the runner accordingly fine I guess you can go with a big sized runner, but just opening up the mouth and leaving the rest the orignal size is a poor thing to do in today's heads.
Maybe he meant gasket matching on the exhaust side which is ok, but without knowing the size of the primaries once again that can prove to be problematic.
And gasket matching is quite possibly the worst thing you can do on the intake side. It opens up the runner and slows down airflow into the rest of the runner. If he enlarged the rest of the runner accordingly fine I guess you can go with a big sized runner, but just opening up the mouth and leaving the rest the orignal size is a poor thing to do in today's heads.
Maybe he meant gasket matching on the exhaust side which is ok, but without knowing the size of the primaries once again that can prove to be problematic.
Staging Lane
Joined: Nov 2012
Posts: 99
Likes: 0
Most of the time people (or porters rather) polish the exhaust runner and/or the combustion chamber. On the intake side it's best to leave a textured/rougher surface rather than a mirror polish.
And gasket matching is quite possibly the worst thing you can do on the intake side. It opens up the runner and slows down airflow into the rest of the runner. If he enlarged the rest of the runner accordingly fine I guess you can go with a big sized runner, but just opening up the mouth and leaving the rest the orignal size is a poor thing to do in today's heads.
Maybe he meant gasket matching on the exhaust side which is ok, but without knowing the size of the primaries once again that can prove to be problematic.
And gasket matching is quite possibly the worst thing you can do on the intake side. It opens up the runner and slows down airflow into the rest of the runner. If he enlarged the rest of the runner accordingly fine I guess you can go with a big sized runner, but just opening up the mouth and leaving the rest the orignal size is a poor thing to do in today's heads.
Maybe he meant gasket matching on the exhaust side which is ok, but without knowing the size of the primaries once again that can prove to be problematic.
